Agricultural combines are large machines that harvest, thresh, separate and clean harvested agricultural crops, such as corn. The resulting clean corn is stored in a corn tank (or “grain tank”) arranged on the combine. Rotary combines are provided with one or two rotors arranged in a rotor housing which are provided for threshing and separating the harvested crop. In most rotary combines the rotor or rotors are arranged along the longitudinal axis of the combine. These rotors are equipped with a charging (or “inlet”) section that accepts harvested crop, which was harvested from the field, a threshing section for the threshing of harvested crop received from the charging section and a separating section for the separating the corn that is still contained in the harvested crop which was received from the threshing section. During the rotation of the rotor the crop is moved in the longitudinal direction from the charging section of the rotor through the threshing section to the separating section. In the separating section the axial movement of the harvested crop is attained by helical guide rails that are arranged underneath the cover element of the rotor housing. The residence time of the harvested crop in the separating section is a function of the inclination of the guide rails, that is, the angle of inclination between the guide rails and the radius of the rotor.
U.S. Pat. No. 4,244,380 proposes that the guide rails be repositioned together on the upper side of the rotor housing in order to make the inclination of the guide rails conform to the type of the crop and its characteristics. The guide rails are fastened with their first ends, free to pivot, about the rotor housing and connected with their second ends with an adjusting rod, that can be slid in the axial direction of the rotor. The sliding of the adjusting rod permits a variation in the inclination of the guide rails. However, these also result in gaps between the guide rails and the rotor housing since the radius of curvature of the guide rails, that are rigid in themselves, may not conform in all positions to the radius of curvature of the rotor housing with which the guide rails are in contact. Harvested crop accumulates in the gaps that may make it difficult or impossible to reposition the guide rails without any previous cleaning of the gap.
Moreover, U.S. Pat. No. 4,258,726, that is seen as forming a class, proposes other possibilities for repositioning guide rails of an axial harvested crop processing arrangement.